In the treatment of heavy hydrocarbons at or near producing wells it is desirable to remove all or virtually all of the water entrained in the oil. In general, water can be removed from the oil simply by heating the mixture to boil the water. However, such boiling for example in a storage tank, results in the evolution of steam which creates large quantities of foam formed from steam bubbles in an oil film. The foaming is, at best, difficult to control and often forms a spill with a volume many times greater than the volume of the liquid.
Apparatus for treating crude oil is known, for example from Canadian Patent No. 1,122,135 issued to Koppers Company, Inc., on Apr. 20, 1982 and U.S. Pat. Nos. 3,441,499 and 3,453,205 both issued to A. W. Francis, Jr. et al on Apr. 26, 1969 and July 1, 1969 respectively. In general, currently available dehydrators rely on differences in the specific gravity of oil and water to effect gravity separation. The gravity separators use a heat source to raise the temperature of the crude oil which reduces the viscosity of the oil to promote phase separation. Such a process is not particularly effective for heavy crude oils which have specific gravities close to that of water. The addition of emulsion breaker have often proved to be of little value.
Other dehydrators utilize vacuum towers combined with heaters for removing water as steam below atmospheric pressure. The vacuum is created by vapor compressors which condense or flare the resulting pressurized steam to the atmosphere. Such a method requires many separate pieces of equipment, is expensive and is best suited to large central plant facilities. Controlled boiling has also been attempted using tray-type towers or expensive heat exchangers.
A further problem in the past is that removal of the water usually leaves residual salts which had been contained in the water, resulting in corrosion. Such salts can accumulate in the apparatus, clogging the tubing and other parts, as well as causing corrosion thereof.
Therefor, a primary object of the present invention is to provide a relatively simple, easy to operate apparatus which can be located in remote oil producing areas for dehydrating crude oil.
Another object of the invention is to provide a method of dehydrating oil which is relatively easy to carry out even in remote areas.
Still another object of the invention is to provide a method and apparatus in which the incoming crude oil is heated at the surface of a bath of crude oil, in such a manner as to minimize the temperature gradient within the bath itself as further crude oil is introduced into the bath.
Yet a further object of the invention is to provide a method and apparatus in which the primary heat transfer between cooler, incoming crude oil and the already heated bath occurs at the surface of the bath of crude oil rather than to a significant depth in the bath, so the temperature gradient within the bath itself is minimized.
Another object of the invention is to provide a method and apparatus for dehydrating crude oil which may employ preliminary separating steps for improving the quality of the incoming crude oil even before it enters the apparatus of the invention for further improving the results of the invention.
A further object of the invention is to provide a method and apparatus for dehydrating crude oil in which a portion of the dehydrated crude oil produced may be recycled, if desired, to the beginning of the process and mixed with crude oil prior to its introduction into the heating chamber for pre-heating incoming crude, thereby further minimizing the temperature gradient within the heating chamber and minimizing the amount of heat required to be added to the system.
These and other objects and advantages of the present invention will become apparent from a further consideration of the details of the invention which follow.